fixes #5264 (#5520); inheriting from generic object

tests/types/tparameterizedparent2.nim

@@ -0,0 +1,77 @@
+discard """
+  output: '''(width: 11, color: 13)
+(width: 15, weight: 13, taste: 11, color: 14)
+(width: 17, color: 16)
+(width: 12.0, taste: yummy, color: 13)
+(width: 0, tast_e: 0.0, kind: Smooth, skin: 1.5, color: 12)'''
+"""
+# bug #5264
+type
+  Texture = enum
+    Smooth
+    Coarse
+
+  FruitBase = object of RootObj
+    color: int
+
+  Level2Fruit = object of FruitBase
+    taste: int
+
+  AppleBanana = object of Level2Fruit
+    weight: int
+
+  BaseFruit[T] = object of RootObj
+    color: T
+
+  Apple[T] = object of T
+    width: int
+
+  Peach[X, T, Y] = object of T
+    width: X
+    taste: Y
+
+  Lemon[T] = object of T
+    width: int
+    tast_e: float64
+    case kind: Texture
+    of Smooth:
+      skin: float64
+    of Coarse:
+      grain: int
+
+var x: Apple[FruitBase]
+x.color = 13
+x.width = 11
+echo x
+
+proc setColor(self: var FruitBase, c: int) =
+  self.color = c
+
+proc setTaste[T](self: var Apple[T], c: int) =
+  self.taste = c
+
+#proc setColor[T](self: var BaseFruit[T], c: int) =
+#  self.color = c
+
+var y: Apple[AppleBanana]
+y.setColor(14)
+y.setTaste(11)
+y.weight = 13
+y.width = 15
+echo y
+
+var w: Apple[BaseFruit[int]]
+w.width = 17
+w.color = 16
+echo w
+
+var z: Peach[float64, BaseFruit[int], string]
+z.width = 12
+z.taste = "yummy"
+#z.setColor(13) #this trigger other bug
+z.color = 13
+echo z
+
+var k = Lemon[FruitBase](kind: Smooth, skin: 1.5)
+k.setColor(12)
+echo k